When you create a new menu item, lets say to your mainmenu, click menu type, and you will see many types of menu types you can create. There is a section of K2, item, caegory, tag, etc
Usually a category is selected which will display all the k2 items in a category according to the category paramaters you have set. Look thru all the category param settings and you will see item view in category, and item view. Set them to display as you like.
You might also look at the menu links on the template makers demo which show K2 item, category, user, etc views linked from menu choices. Joomlabamboo.com and gavick.com both have demos of their templates with k2 links.